Bench testing an EGR solenoid 1990 454SS

TheRealAlBoudreau · Jul 24, 2024

Looking for some guidance. I need to bench test an EGR solenoid. I can't do it in the truck as it's not running at the moment. Don't want to dump $$ if the one I have is fine. I simply want to rule it in or out.

What is the procedure to test it?

Thank you.

someotherguy · Jul 24, 2024

Test procedures for the EGR system will be in the factory service manuals, free downloads of them available here linked in the sticky posts at the top of the forum. Look up your particular year and download that manual.

Why is the truck not running? Curious why the EGR solenoid would be the focus at the moment if the engine isn't running. I wouldn't suspect EGR system to be related to anything other than driveability symptoms.

Richard

TheRealAlBoudreau · Jul 24, 2024

Hi Richard
I'm going through the truck right now just to make sure all parts are working. I understand that the EGR solenoid would not impact the operational status.
Currently, the truck starts and runs only when i'm actively feathering the throttle. If I let off, it runs for a second or two then dies. If I try to simply keep the RPM at a certain level, it dies. I have to actively rev it.
Next step i'll be taking will be measuring the fuel pressure coming from the pump. I'm concerned about the pressure regulator on the TBI not working properly. I have one from a 93 chevy caprice that fits and is supposed to be the same fuel pressure, so, i'll try that and see. (part# GM Part # 19143609)
I've done the reset of the IAC motor and adjust the idle screw. Actually, you might know this: how much should the idle screw be in when setting a base setting?

I appreciate the help.
The manual I got from here does show much.

Al

someotherguy · Jul 24, 2024

I don't know if there's a specified base setting for the minimum air rate screw; does the manual say anything other than to warn you not to mess with it because it's sealed and not supposed to be adjustable? Generally, you should never need to adjust it, but I do understand there's situations where it can help. If it's still sealed, I wouldn't dig in there and adjust it until all other potential causes for a low idle have been addressed.

This is the second time in the last 5 minutes I've said "I could be wrong" in a reply on this forum so that feels kinda weird.. but I do believe the optimal setting for minimum air rate has the throttle blades almost completely closed, if not completely closed. The IAC should be doing most of the work here. When the IAC is fully responsible for the idle, the ECM has more range of control than if you've set a mechanical open position for it via the screw.

Richard

TheRealAlBoudreau · Jul 24, 2024

Hi Richard.
The hole was not sealed when we got the truck. The previous owner had the truck sitting for years because he could not get it to run reliably. I do not know what was done so I'm attempting to get everything to a known good state and go from there
I replaced the IAC and the TPS just to be sure. New plugs, cap, rotor, wires, plugs as well.
The pickings in the manuals sticky are thin for the 1990 edition. The one manual is only a teardown and rebuild manual.
What steps would you take next?

someotherguy · Jul 24, 2024

If there's not a factory service manual for 1990 uploaded, I'd try 1991-1992 as they would be the closest to same, at least in terms of underhood and engine controls. Underdash wiring gets very different for 1992 as the gauge cluster electronics changed significantly.

Of course 1988-1989 are very similar to your 1990, and in terms of factory manual would be very close, although the 454SS didn't exist just yet - there will be 454-related info for the 3/4 and 1 ton trucks but again may be equipment differences based on that.

Richard

TheRealAlBoudreau · Jul 24, 2024

So, it turns out that my fuel pump is not providing the appropriate fuel pressure. Hooked up a remote fuel source with the appropriate pressure and truck idles AND roars.

Bench testing an EGR solenoid 1990 454SS

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